A backlight module is commonly employed to illuminate a liquid crystal display panel in an LCD. In general, backlight modules include a light guide plate and a light source to supply light to the light guide plate. Although tubular fluorescent lamps such as cold cathode fluorescent lamps (CCFLs) have been widely adopted as light sources, a recent tendency in adopting alternative light sources using point light emitters such as light emitting diodes (called LEDs hereafter) are growingly popular. Two or more LEDs are generally provided as a light source in a backlight module so that enough light is generated.
FIG. 1 and FIG. 2 represents a backlight module 10 including the light source and a light guide plate 13. The light guide plate 13 includes an incident surface 131, an emitting surface 132 adjoining to the incident surface 131, and a bottom surface 133 opposite to the emitting surface 132. The light source includes three light emitters 12 such as LEDs. The light emitters 12 are positioned besides the light guide plate 13 and face the incident surface 131. Light rays emitted from the light emitters 12 enter the light guide plate 13 via the incident surface 131, and are reflected and refracted in the light guide plate 13 until finally emitted out of the light guide plate 13 via the emitting surface 132. However, a plurality of dark areas 15 exist on the emitting surface 132 corresponding to positions between any two light emitters 12 because less light rays projects onto these areas. Thus, the backlight module 10 has a low optical uniformity.
What is needed, therefore, is a light guide plate and a backlight module using the same which can improve their optical brightness and optical uniformity.